Semiconductor device characteristics measurement apparatus and connection apparatus

ABSTRACT

A semiconductor-device characteristic measurement apparatus includes first measuring means for measuring a first electrical characteristic of a device under test, second measuring means, switching means for switching between the first measuring means and the second measuring means such that one of the measuring means is connected to the device under test, and controlling means for controlling the switching means. The switching means includes switches that switch between a first wiring configuration for electrically connecting the first measuring means to the device under test and a second wiring configuration for electrically connecting the second measuring means to the device under test. The switching means is electrically connected to the device under test at a position closer to the device under test than the first measuring means and the second measuring means.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a measurement apparatus for anelectronic device. More specifically, the present invention relates to ameasurement apparatus for semiconductor device characteristics of anintegrated circuit device or discrete electronic circuit device, and toa connection apparatus used for such measurement.

2. Description of the Related Art

Conventionally, the related technologies shown in FIGS. 1 and 2 havebeen known as apparatuses for measuring the electrical characteristicsof a device to be tested (or “device under test”, hereinafter referredto as DUT), such as integrated circuit devices and discrete electroniccircuit devices consisting of semiconductors.

FIG. 1 shows a known example of an apparatus for measuring electricalcharacteristics by causing a probe apparatus 100 to probe a DUT 50. Inthis known example, a current-voltage characteristic measurement unit 20(or a source monitor unit or a source measure unit, which is hereinafterreferred to as an “SMU”), an LCR (inductance-capacitance-resistance)meter 22, and a pulse generator 24, which are independent apparatuses,are provided in an equipment rack 200. In the SMU 20, a direct-currentvoltage source, a current source, a voltmeter, and an ammeter areintegrated so as to be usable in an arbitrary combination. The LCR meter22 can measure inductance, electrical capacitance, and resistance. Thepulse generator 24 generates a pulse to be applied to the DUT 50. TheSMU 20, the LCR meter 22, and the pulse generator 24 are connected tothe probe apparatus 100, which probes specific electrical contacts andso on of the DUT 50, via respective independent measurement cables. Inthe known example, when measuring a different characteristic of the DUT50, an operator manually replaces the wires used for measuring the DUT50 to perform the measurement. Thus, this example has the advantage ofbeing able to carry out measurement accurately, since an appropriateconfiguration can be used for each type of measurement. However, theexample also suffers from the drawback that measurement operation isinefficient, since the operator needs to manually replace theconnections.

FIG. 2 shows another known example in which a switching matrix 300 iscombined with the SMU 20, the LCR meter 22, the pulse generator 24, andso on to perform measurement. In this example, appropriate control ofthe switching matrix 300 allows various types of measurement to beautomatically performed. This configuration, however, has a problem inthat it is difficult to accurately measure the electricalcharacteristics of the DUT 50. In addition, U.S. Pat. No. 6,069,484discloses a technique that connects a plurality of SMUs via a switchingmatrix.

SUMMARY OF THE INVENTION

An object of the present invention is to accurately measure electricalcharacteristics of a DUT without the need for manually switchingconnections. In particular, the present invention is directed to, but isnot limited to, a series of measurements, such as when multiplemeasurement items are switched for measurement.

The present inventors have discovered that the problems of the knownexamples result from the following causes. Namely, when a switchingmatrix is used for switching, the switching matrix is placed far from aDUT, so that the return current of a measurement signal is delayed intime or returns after making a detour. In addition, the feedback currentpath is connected to the feedback path of another measuring means. For aso-called Kelvin connection scheme, with a matrix structure used in theknown technology, the outer shield conductor of a measurement cable isgrounded at the entrance of the signal switching matrix. Further, thephysical form of the matrix portion is large and thus a connection cablefrom the exit of the matrix to the DUT needs to be extended. Thus, theresistance, self-inductance, and mutual inductance of such cable affectthe measurement.

The present invention provides a semiconductor device characteristicsmeasurement apparatus. The measurement apparatus comprises: firstmeasuring means for measuring a first electrical characteristic of aDUT, which is a semiconductor device; and second measuring means formeasuring a second electrical characteristic of the DUT. The measurementapparatus further comprises switching means for switching between thefirst measuring means and the second measuring means such that one ofthe measuring means is connected to the DUT; and controlling means forcontrolling the switching means by supplying a control signal. Theswitching means comprises at least one switch that switches between afirst wiring configuration for electrically connecting the firstmeasuring means to the DUT and a second wiring configuration forelectrically connecting the second measuring means to the DUT inaccordance with the control signal supplied from the controlling means.The first wiring configuration is suitable for measuring the firstelectrical characteristic and the second wiring configuration issuitable for measuring the second electrical characteristic. Theswitching means is electrically connected to the DUT at a positioncloser to the DUT than the first measuring means and the secondmeasuring means.

The present invention provides a connection apparatus for connecting ameasurement apparatus and a DUT, which is a semiconductor device. Theconnection apparatus comprises switching means, connected to the DUT,for receiving a control signal from controlling means; a preamplifierconnected to the switching means; first connectors that are connected tothe preamplifiers and that are connectable to first measuring means formeasuring a first electrical characteristic of the DUT; and at least onesecond connector that is connected to the switching means and that isconnectable to second measuring means for measuring a second electricalcharacteristic of the DUT. The switching means comprises at least oneswitch that switches between a first wiring configuration forelectrically connecting the first measuring means to the DUT via thefirst connectors and the preamplifiers and a second wiring configurationfor electrically connecting the second measuring means to the DUT viathe second connector in accordance with the control signal from thecontrolling means. The first wiring configuration is suitable formeasuring the first electrical characteristic and the second wiringconfiguration is suitable for measuring the second electricalcharacteristic. The preamplifiers amplify current signals and/or voltagesignals for the first measuring means.

When the measurement apparatus or the connection apparatus according tothe present invention is used, various electrical characteristics can bemeasured in combination or by switching the characteristics. Examples ofpossible measurement include capacitance measurement for measuring thefilm-thickness of a gate oxide film of a MOS (metal oxide semiconductor)device and leakage-current measurement of the gate oxide film,inter-wire capacitance measurement of a wiring component of anintegrated circuit device and inter-line leakage current measurementthereof, junction-capacitance measurement and IV (current-voltage)characteristic measurement of a bipolar transistor,multiple-electrical-characteristics measurement for evaluating theperformance of a floating gate of a flash memory device, andcharacteristics measurement for evaluating deteriorating characteristicsby applying various pulses when stress is applied to an integratedcircuit device. The DUTs may take various forms, such as integratedcircuit devices fabricated with a silicon wafer or the like, a TEG (testelement group) for evaluating an integrated-circuit-device manufacturingprocess, or non-integrated discrete devices (e.g., transistor devices).A probe apparatus can be used for integrated circuits or the like and afixture can be used for discrete devices.

In the measurement apparatus of the present invention, preferably, theswitching means further comprises micro-current detecting means fordetecting micro current flowing in the DUT. The switching means canswitch among the first wiring configuration, the second wiringconfiguration, and a third wiring configuration in accordance with thecontrol signal supplied from the controlling means. The third wiringconfiguration can electrically connect at least one of the firstmeasuring means and the second measuring means to the micro-currentdetecting means, can electrically connect the micro-current detectingmeans to the DUT, and is suitable for measuring the micro current in theDUT. In the connection apparatus of the present invention, preferably,the preamplifiers may comprise micro-current detecting means foramplifying the current signals.

For measuring micro current, the switching means and the connectionapparatus detect the micro current and the first measuring means and soon measure a transmission signal corresponding to the micro current. Asa result, a path for detecting micro current that is susceptible tonoise and so on is limited to a section between the DUT and theswitching means and/or the connection apparatus. This makes it possibleto measure micro current with accuracy.

When the first wiring configuration electrically connects the firstmeasuring means to the DUT, the first wiring configuration, a firstsignal path from the first measuring means to the DUT may be accompaniedby a first feedback path from the DUT to the first measuring means. Thefirst feedback path corresponds to the first signal path. When thesecond wiring configuration electrically connects the second measuringmeans to the DUT, a second signal path from the second measuring meansto the DUT may be accompanied by a second feedback path from the DUT tothe second measuring means. The second feedback path corresponds to thesecond signal path.

An effective wiring configuration can be employed for the measuringmeans and the DUT, in accordance with the characteristics measured bythe measuring means. For example, a Kelvin connection scheme iseffective for measurement using a source monitor unit (SMU), and afour-pair-terminal configuration is effective for measurement using anLCR meter. In the present invention, such wiring configurations can beprovided when the connection means is connected to the DUT via theswitching means. Thus, when the switching means switches connections,measurement that is suitable for each measuring means can be performed.

In the measurement apparatus or the connection apparatus of the presentinvention, the switching means may comprise a first switching portionincluded in a first signal path connected to one terminal of the DUT anda second switching portion included in a second signal path connected toanother terminal of the DUT. The first switching portion and the secondswitching portion can operate in conjunction with each other undercontrol of the controlling means to switch between the first wiringconfiguration and the second wiring configuration.

The first switching portion and the second switching portion operate asthe switching means in conjunction with each other by switching betweensignal paths connected to different terminals of the DUT. Thus, forexample, when a probe apparatus or the like that has probe pins forcorresponding different terminals of a DUT is used, the switchingportions can be provided for respective signal paths via which signalsare applied to the probe pins. Such a configuration makes it possible touse, for example, a configuration in which the length of wires in theprobe apparatus is minimized, thereby allowing for high-accuracymeasurement.

In the measurement apparatus or the connection apparatus of the presentinvention, the first switching portion and the second switching portionmay have signal feedback terminals that are connectable with each other.

Connecting the ground terminals of the first and second switchingportions provides a ground potential that is common to the first andsecond switching portions, resulting in a high accuracy measurement.

In the measurement apparatus or the connection apparatus of the presentinvention, the controlling means may be arranged together with at leastone of the first measuring means and the second measuring means tocontrol the switching means.

With this arrangement, the controlling means for controlling the firstmeasuring means or the second measuring means can be used as controllingmeans for controlling the switching means. This makes it possible toprovide a simplified configuration that can operate in conjunction withthe controlling means.

In the measurement apparatus or the connection apparatus of the presentinvention, the controlling means can synchronize with operation of atleast one of the first measuring means and the second measuring means toperform control such that the switching means performs a switchingoperation.

For example, when the first measuring means starts measurement, theswitching means switches the configuration to the first wiringconfiguration in synchronization, and when the second measuring meansstarts measurement after stopping the measurement performed by the firstmeasuring means, the switching means switches the configuration to thesecond wiring configuration in synchronization. This allows forappropriate switching between measurements performed by the firstmeasuring means and the second measuring means.

In the measurement apparatus of the connection apparatus of the presentinvention, one of the first measuring means and the second measuringmeans can comprise at least one of an impedance measurement unit, apulse generator, and a current-voltage characteristic measurement unit.

The impedance measurement unit can be, for example, an inductance meterthat measures inductance L, capacitance C, and resistance R. The sourcemonitor unit (SMU) can be a unit in which a direct-current voltagesource, current source, voltmeter, and ammeter are integrated so as tobe usable in an arbitrary combination. With such a configuration,equipment provided with an impedance measurement unit, a pulsegenerator, and a source monitor can be used to perform measurementthrough appropriate switching while maintaining measurement accuracy.

The present invention further provides a connection apparatus. Theconnection apparatus comprises a first triaxial connector and a secondtriaxial connector that are to be connected to a DUT, which is asemiconductor device; a first coaxial connector, a second coaxialconnector, and a third triaxial connector that are to be connected tomeasuring means for measuring an electrical characteristic of the DUT;and micro-current detecting means having a first output, a secondoutput, a first input, a second input, resistors connected to the firstinput, and buffer amplifiers for transmitting respective voltages acrossthe resistors to the first output and the second output. The connectionapparatus further comprises switching means for switching betweenconnection configurations connected to the first coaxial connector, thesecond coaxial connector, and the third coaxial connector; and a controlinput terminal that is connectable to controlling means for controllingthe switching means. For measuring alternating current, under control ofthe controlling means through the control input terminal, the switchingmeans establishes connections such that core lines of the first andsecond coaxial connectors are interconnected and are connected to thecore line of the first triaxial connector, and outer shield conductorsof the first and second coaxial connectors are interconnected and areconnected to guard conductors of the first and second triaxialconnectors. Each guard conductor is disposed between the core line andan outer shield conductor of each triaxial connector. For measuringdirect-current voltage current, the switching means establishesconnections such that a core line of the third triaxial connector isconnected to the core line of the first triaxial connector, the coreline of the second triaxial connector is connected to the first outputvia the second input of the micro-current detecting means, and a guardconnector of the third triaxial connector is connected to the guardconductors of the first and second triaxial connectors. For measuringmicro current, the switching means establishes connections such that thecore line of the first triaxial connector is connected to the firstinput of the micro-current detecting means to cause the bufferamplifiers to output the respective voltages across the resistors asfirst and second outputs.

The connection apparatus having the configuration described above isconnected to the DUT via the first and second triaxial connectors and isconnected to the measuring means via the first coaxial connector, thesecond coaxial connector, and the third triaxial connector. Further, anexternal controlling means can be employed to switch among measurementof the alternating current, DC-voltage current or the micro currentusing the measuring means. Depending on the measurement to be carriedout, a single connection apparatus having the configuration describedabove can be used to connect the device under test and the measuringmeans, or multiple connection apparatuses having the same configurationdescribed above can be used so that they are provided to form pairs withthe respective measurement electrodes of the DUT and respectivemeasurement units.

According to the present invention, it is possible to configure ameasurement system that offers enhanced convenience in measurement andthat provides increased measurement accuracy compared to the knownexamples described above. In addition, since the micro-current detectingmeans is located in the vicinity of the DUT, it is possible toaccurately measure a minute current range as small as femto-amperes orless.

When the connection apparatus is connected to a pulse generator, awaveform with less distortion can be supplied to the DUT duringmeasurement with the pulse generator. When the SMU performs power supplyand control for the switching portions, it is possible to efficientlyswitch between DC measurement performed by the SMU and measurementperformed by the LCR meter, thereby preventing the switching functionfrom adversely affecting the micro-current measurement function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a knownsemiconductor-device characteristic measurement apparatus;

FIG. 2 is a block diagram showing the configuration of a knownsemiconductor-device characteristic measurement apparatus using aswitching matrix;

FIG. 3 is a block diagram showing the configuration of asemiconductor-device characteristic measurement apparatus according toan embodiment of the present invention;

FIG. 4 is a block diagram showing a configuration of switching means inthe embodiment of the present invention;

FIG. 5 is a block diagram showing the configuration of a measurementapparatus and a connection apparatus when an LCR meter and an SMU areused in the embodiment of the present invention;

FIG. 6 is a block diagram showing the connection of the measurementapparatus and the connection apparatus when the LCR meter in theembodiment of the present invention performs measurement;

FIG. 7 is a block diagram showing the connection of the measurementapparatus and the connection apparatus when the SMU in the embodiment ofthe present invention performs measurement;

FIG. 8 is a block diagram showing the configuration of a micro-currentdetector in the switching means in the embodiment of the presentinvention;

FIG. 9 is a block diagram showing the connection of the measurementapparatus and the connection apparatus when a pulse generator in theembodiment of the present invention performs measurement;

FIG. 10 is a block diagram showing the connection of the measurementapparatus and the connection apparatus when the pulse generator in theembodiment of the present invention performs measurement via a singlechannel;

FIG. 11 is a block diagram showing the configuration of a connectionapparatus, which uses preamplifiers, according to an embodiment of thepresent invention; and

FIG. 12 is a block diagram showing another configuration of theswitching means in the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention will bedescribed below with reference to the accompanying drawings.

[Basic Configuration]

FIG. 3 is a block diagram showing the configuration of an embodiment formeasuring capacitance in the present invention. FIG. 3 shows a blockconfiguration in which an SMU (source monitor units or source measureunit) 20, an LCR (inductance-capacitance-resistance) meter 22, and apulse generator 24, which are mounted in an equipment rack 200, are usedto measure electrical characteristics of a DUT (device under test) 50.The DUT 50 is mounted on a probe apparatus 100 so as to be probed. Forconvenience, the terms “positive (+) side” and “negative (−) side” areused for terminals of the DUT 50 and apparatuses to distinguish betweenits connections therewith. These expressions, however, are notparticularly intended to mean a high potential and a low potential.

A switching portion 12 has an atto (attoampere) sense unit 12P(hereinafter referred to as an “ASU”), used for connection with thepositive side of the DUT 50, and an SMU 12M, used for connection withthe negative side of the DUT 50. The ASUs 12P and 12M have built-infunctions for enabling switching and also functions (provided bymicro-current detecting means) for measuring micro current.

The SMU 20 is a unit in which a direct-current voltage source, currentsource, voltmeter, and ammeter are integrated so as to be usable in anarbitrary combination. The SMU 20 typically has two operation modes. Oneis a mode in which a voltage is applied to measure a current and theother is a mode in which current is applied to measure a voltage. TheSMU 20 has a first channel and a second channel, both of which arecombined to perform measurement. The SMU 20 may include a controller(i.e., controlling means) 202 for controlling the ASU 12. In such acase, the controller 202 is connected to the ASUs 12P and 12M via cables214 and 218 so as to control the ASUs 12P and 12M. Each of the first andsecond channels of the SMU 20 has two types of connection terminals,i.e., a force terminal and a control terminal, in order to realizeKelvin connection. The force terminals can be connected to triaxialcables, and the control terminals include current detection lines andsupply power to and control the ASU 20. A typical SMU uses forceterminals and sense terminals to perform measurement, but the SMU 20 inthe present embodiment does not use sense terminals. Alternatively, thecontrol terminals include the current detection lines to allowmeasurement.

The force terminal of the first channel of the SMU 20 is connected tothe ASU 12P via a cable 212 and the control terminal of the firstchannel is connected via the cable 214. The force terminal of the secondchannel of the SMU 20 is connected to the ASU 12M via a cable 216 andthe control terminal of the second channel is connected via the cable218.

The LCR meter 22 is measuring means that can typically measure impedanceand can measure L (inductance), C (capacitance), and R (resistance) forvarious applied waveforms and under various conditions. That is, the LCRmeter 22 is measuring means that can serve as inductance measuringmeans, capacitance measuring means, and resistance measuring means. TheLCR meter 22 is connected to the ASU 12P and the ASU 12M via a positive(high) side current cable 222, a positive (high) side voltage cable 224,a negative (low) side current cable 226, and a negative (low) sidevoltage cable 228.

The pulse generator 24 is means that can generate various pulse voltagesto be applied to the DUT 50. The pulse generator 24 is connected to theASU 12P and the ASU 12M via a positive-side cable 24P and anegative-side cable 24M, respectively.

The DUT 50 is, but is not limited to, a semiconductor device, such as atransistor, or a device of a TEG (test element group) or the likefabricated with a silicon wafer and used for determining the optimumprocess conditions for manufacturing integrated circuits. The DUT 50 isconnected to the ASU 12P via cables 30F and 30S and is also connected tothe ASU 12M via cables 32F and 32S.

As shown in FIG. 3, what are used in the present embodiment are thefirst measuring means (i.e., the SMU 20) for measuring an electricalcharacteristic of the DUT 50, the second measuring means (i.e., the LCRmeter 22 or the pulse generator 24) for another electricalcharacteristic of the DUT 50, and the switching portion 12 (i.e., theASUs 12P and 12M) that is connected to the controlling means (i.e., thecontroller 202) and that has micro-current detecting means (i.e., amicro-current detector 102 shown in FIG. 4). The switching portion 12 isplaced in the probe apparatus 100 at a position that is far from thosemeasuring means and that is the closest to the DUT 50, and iselectrically connected to the DUT 50. The switching portion 12 is alsoelectrically connected to the multiple measuring means via the cables toswitch between the first measuring means and the second measuring meanssuch that one of the measuring means is electrically connected to theDUT 50, in accordance with a control signal supplied from thecontrolling means (i.e., the controller 202). The switching portion 12,which has the micro-current detectors 120, can be connected to ground atthe probe apparatus 100.

Although FIG. 3 shows a case in which all the measurement units mountedin the equipment rack 200 are connected to the DUT 50 via the probeapparatus 100, the present invention also includes the case, asdescribed below, where two measurement units required for measurementare connected to the DUT 50. That is, the present invention alsoincludes the case in which any two of the three illustrated measuringunits are used.

The configuration of the ASUs 12P and 12M of the switching portion 12will now be described with reference to FIG. 4. The use of the ASUs 12Pand 12M allows a switching operation between, for example, (1) themeasurement of voltage and current using the SMU 20, (2) the measurementof capacitance using the LCR meter 22, and (3) the measurement of pulsesusing the pulse generator 24.

The ASUs 12P and 12M have a switching function and also have therespective micro-current detectors 120. The switching function isachieved by selectively opening closing connection pieces included inrelay switches S1 to S8. These switches S1 to S8 are controlled by thecontrolling means 202 (shown in FIG. 3). Referring to FIG. 3, the cables214 and 218, which extend from the SMU 20, represent control signallines. A connector 120C provides connection for a control line, notshown, between the controlling means 202, which controls the switches S1to S8, and the corresponding ASU 12P or 12M. Further, a line that servesas an output for the micro-current detector 120 and that serves as aninput for the SMU 20 is connected to the connector 120C. FIG. 4illustrates only a line 120L that couples the connector 120C and themicro-current detector 120, but lines for controlling the switches S1 toS8 are also included in the present embodiment. The relay switches S1 toS8 of ASU 12P and 12M switch between electrical connection andelectrical insulation for connectors 122L+, 122L−, 122P, and 122S(connecting means) located at the measuring-means side, connectors 124Fand 124S, the micro-current detector 120, and ground 126, which arelocated at the DUT 50 side. In particular, the embodiment of the presentinvention can also switch between current feedback paths for thosemeasuring means at the same time when performing switching between thesignal paths. In this manner, the feedback paths that accompany thesignal paths allow feedback current to be appropriately fed back tointended paths. Further, the micro-current detector 120 has a functionfor sensing micro current. A connection terminal 120 a is also provided,such that it forms a feedback path for the measuring means that isconnected to the connectors 122L+ and 122L−, when the connector 124S isnot connected.

FIG. 4 illustrates the configuration of ASUs to which three measuringmeans, as shown in FIG. 3, are connected. However, when two measuringmeans are connected to the ASUs at the same time, some inputs at themeasuring means can be eliminated. The configuration of such a case isshown in FIG. 12. In the configuration shown in FIG. 12, the connector122P, the switches S3 and S4, and the connection lines coupling theconnector 122P and the switches S3 and S4 are not provided. In thiscase, a function equivalent to that of the connector 122P and theswitches S3 and S4 is realized by the switches S1 and S2 and either theconnector 122L+ or the connector 122L−.

In the present invention, it is also possible to measure a current largeenough not to require the use of the micro-current detectors 120. Inthis case, a wiring configuration for measurement using the SMU 20 isemployed. The wiring configuration for measurement using themicro-current detectors 120 and the wiring configuration for measurementusing the SMU 20 can be switched by opening closing the switches S5 andS6. The controller 202 of the SMU 20 controls the supply of power to themicro-current detectors 120 of the ASUs 12P and 12M, the supply ofoperation power to the switches, and the operation of the switches.

[For Impedance Measurement]

An example for measuring impedance using the LCR meter 22 and the SMU 20in the present embodiment will now be described with reference to FIGS.5 to 7. FIG. 5 shows the circuit configuration of this example and FIG.6 illustrates the operation of the ASUs 12P and 12P when the LCR meter22 is used to perform measurement. FIG. 7 illustrates an operation whenthe SMU 20 is used to perform measurement. Although the connector 122Pand the relay switches S3 and S4 are not shown in the figuresillustrated below as in FIG. 12, the connector 122P and the relayswitches S3 and S4 may also be included and such a configuration alsoallows the ASUs to perform switching in the present embodiment. Also,the probe apparatus 100 and the equipment rack 200 are not shown.

In the present embodiment shown in FIGS. 5 and 6, for example, an LCRmeter for performing four-terminal-pair measurement can be used, such asAgilent 4284A manufactured by Agilent Technologies Inc. The LCR meter 22has an HC (high current) connector 222C for supplying analternating-current (AC) signal to the high (+) side connector of theDUT 50; an HP (high potential) connector 224C for monitoring a voltageat the high-side connector of the DUT 50; an LC (low current) connector226C, connected to the low (−) side of the DUT 50, for measuring currentflowing therethrough; and an LP (low potential) connector 228C formonitoring a voltage at the low (−) side connector of the DUT 50. In thepresent embodiment, the connectors 222C and 224C are connected to theASU 12P via cables 222 and 224, respectively, and the connectors 226Cand 228C are connected to the ASU 12M via cables 226 and 228,respectively.

In the LCR meter 22, coaxial cables can be used for the cables 222 and228 connected to the corresponding connectors 222C and 228C. In thiscase, the configuration is such that feedback currents for theconnectors 222C to 228C are returned to the LCR meter 22 via therespective outer shield conductors of the coaxial cables 222 to 228.Thus, the current in the center conductor and the current in the outershield conductor flow in directions opposite to each other and are thesame in magnitude. In this case, since the magnetic fields generated byboth currents cancel each other out, no magnetic field is generatedaround the conductors. That is, no magnetic field is induced by themeasurement-signal current. Thus, error is not increased by the selfinductance of measurement paths to the DUT 50 or the mutual inductanceof the lead lines, so that measurement can be accurately performed. Inthe present embodiment, coaxial cables may be used for the cables 222 to228. In the LCR meter 22, the center conductor and the outer shieldconductor of the LC connector 226C have voltages that are bothmaintained at ground potential by an automatic bridge circuit. The LCRmeter 22 determines the ratio of a DUT-terminal voltage observed at theHP connector 224C to a DUT current observed at the LC connector 226C. Asa result, the impedance of the DUT 50 can be determined.

Also, a pair of lines coupled to the center conductors of the HCconnector 222C and the HP connector 224C and a pair of lines coupled tothe center conductors of the LC connector 226C and the LP connector 228Cmay be connected, in close vicinity of the DUT 50, to the positive-sideconnector and the negative-side connector of the DUT 50, respectively.This arrangement can avoid measurement errors caused by a drop involtages generated by the resistances of the cables and measurementcurrents (typically, such measurement is called four-terminal-pairmeasurement).

Next, current paths for a case in which the LCR meter 22 is used toperform measurement in the present invention will be described withreference to FIG. 6. In the present embodiment, the cables 30F, 30S,32F, and 32S used for performing measurement on the DUT 50 are triaxialcables, which have a structure in which three types of conductors arecoaxially arranged. Specifically, each of the cables 30F, 30S, 32F, and32S has a center conductor 302 disposed at the center, a tube-shapedouter shield conductor 304 that covers the outmost side of the cable,and a tube-shaped guard conductor 306 that is disposed inside the outershield conductor and outside the center conductor 302 and that coversthe center conductor 302.

In the present embodiment, the controlling means 202 of the SMU 20controls the opening and closing of the relay switches S1 to S8 of theASUs 12P and 12M via the cables 214 and 218. In this case, thecombination of the opening and closing of the relay switches S1 to S8 isadapted to form a feedback path such that all feedback current returnsto the LCR meter 22. That is, current that is applied and flows in thecenter conductor of the coaxial cable 222, which is connected to the HCconnector 222C shown in FIG. 6, flows to the center conductor 302 of thetriaxial cable 30F via a channel formed by closing the switches S1 andS2 in the ASU 12P. The current is supplied to a positive-sidemeasurement portion 502 of the DUT 50 via a probe pin of the probeapparatus 100. Feedback current for the HC connector 222C flows throughthe switch S9 disposed adjacent to the DUT 50 and returns to the HCconnector 222C via the guard conductor 306 of the triaxial cable 30F.The current then flows through a channel formed by closing the switch S1and returns to the HC connector 222C via the outer shield conductor ofthe coaxial cable 222. The center conductor of the cable 224, which isconnected to the HP connector 224C, is electrically connected to aconnection path that leads to the center conductor of the coaxial cable222 via the switch S1. The outer shield conductor of the cable 224,which is connected to the HP connector 224C, is electrically connected,inside the ASU 12P, to the outer shield conductor of the cable 222. Theswitches are controlled as described above to provide a wiringconfiguration suitable for measuring the LCR meter 24. As a result, itis possible to accurately measure a voltage via the HP connector 222C.

In the same manner in which the HC connector 222C and the HP connector224C are connected to the positive-side measurement portion of the DUT50 and the switch S9, the LC connector 226C and the LP connector 228Care connected to a negative-side connection portion 504 of the DUT 50and the switch S9 via the ASU 12M that is in the same state as the ASU12P.

Thus, the paths of the applied current, feedback current, and thevoltage measurement portions of a case in which the LCR meter 24 isconnected to the ASU 12P and the ASU 12M are analogous to those when theLCR meter 24 is individually used. In particular, as shown in FIG. 3,when the ASUs 12P and 12M are provided in the probe apparatus 100,additional impedances from the connection points of the currentconnectors, such as the HC connector 222C and the LC connector 226C, andthe potential connectors, such as the HP connector 224C and the LPconnector 228C, to the DUT 50 are considerably reduced compared to theknown case (shown in FIG. 2) in which the switching matrix is used.

In FIG. 6, the outer conductors of the cables 30F and 32F are connectedin close vicinity of the DUT 50 to the switch S9 in order to realize thefeedback paths. However, to achieve such a connection may be difficultbecause of the mechanical configuration or the like of the apparatus. Insuch a case, instead of the connection described above, binding postconnectors 128P and 128M may be provided at the respective ASUs 12P and12M, which can be interconnected to realize the feedback path (indicatedby a dotted line 128). Such a configuration is also effective when bothof the ASUs 12P and 12M are provided in the probe apparatus 100, sincethe length of feedback-path portions that do not accompany the signallines are shorter than the known case (shown in FIG. 2) in which theswitching matrix is used. The connection as described above alsoprovides an advantage in that the measurement of capacitance and themeasurement of micro current can be switched without opening/closingoperation of the switch S9, as described below.

[For Measuring DC Component]

A case in which a DC (direct current) component is measured in theembodiment of the present invention will now be described with referenceto FIG. 7. In this case, the switch S9 is open. For measuring a DCcomponent, it is possible to perform measurement using detecting meansof the SMU 20 and measurement using the micro-current detectors 120 inthe ASUs 12P and 12M.

First, measurement using the detecting means of the SMU 20 will bedescribed with reference to FIG. 7. The figure shows a connection usedfor the measurement. In FIG. 7, the upper contact of the switch S2 isopen and the lower contact thereof is closed and the upper contact ofthe switch S5 is closed and the lower contact thereof is open. That is,a wire that couples the switches S1 and the S2 is connected to the lowercontact of the switch S2 so as to be electrically connected to aright-side terminal of the switch S2 whose potential is at a guardpotential. With this arrangement, the wire that couples the switches S1and S2 and the DUT 50 are at the same potential. As a result, it ispossible to reduce errors due to potential fluctuation caused byfloating of the wire that couples the switches S1 and S2 and due to theupper-contact induced leakage current caused by the fluctuation. Usingthe first and second channels, the SMU 20 can measure current throughthe application of a voltage to the DUT 50 and can measure a voltagethrough the feeding of current to the DUT 50. A triaxial cable 212 isconnected to the force connector of the first channel of the SMU 20. Acenter conductor 2122 of the triaxial cable 212 transmits a signal forapplying and feeding a voltage and current to the DUT 50. The signal issent to the positive-side terminal of the DUT 50 via the switches S5 andS6, provided in the ASU 12P, and the center conductor 302 of the cable30F. A guard conductor 2126 of the triaxial cable 212 is electricallyconnected to the guard conductor 306 of the triaxial cable 30F via theswitch S7, so that leakage current resulting from the cables can bereduced. A sense signal line is connected to a node 502 at the DUT 50side of the center conductor 304 of the cable 30F. A sense signal at thenode 502 is transmitted through the triaxial cable 30S. The guardconductor of the triaxial cable 30S is electrically connected to theguard conductor 2126 of the triaxial cable 212 via the switch S7, andthe configuration is such that no voltage drop due to leakage currentoccurs.

Measurement using the micro-current detector 120 will be described next.In this case, in FIG. 7, the upper contact of the switch S5 is open andthe lower contact thereof is closed. The cable 214 is connected to thecontrol connector provided at the first channel of the SMU 20. Thecontrol connector is fabricated with, for example, a general-purposecontrol and communication connector, such as a D-sub connector. Thecontrol connector has a current detection line in the wire thereof. Thecurrent detection line is used, instead of the sense terminal of eachchannel of the SMU 20, to receive a sense signal so as to measurecurrent and voltage. The current detection line is connected to themicro-current detector 120 in the ASU 12P.

As shown in FIG. 8, the micro-current detector 120 has first bufferamplifiers 1210 and 1212 and a second buffer amplifier 1202. The twofirst buffers amplifiers, i.e., the buffer amplifiers 1210 and 1212, areconfigured such that they can be switched by a switch S10 to change ameasurement range. In operation, it is sufficient so long as one of thebuffer amplifiers 1210 and 1212 is used. FIG. 8 shows the connection ofrelays for a case in which a measurement range using the bufferamplifier 1210 is selected. A force voltage is applied from the SMU 20(not shown) to a terminal 1214 via the cable 214 or 218. The voltage isthen transmitted to the core line of the connector 124F adjacent to theDUT 50 via a buffer amplifier 1204 or 1206 corresponding to themeasurement range. For respective measurement ranges, super-highresistors 1204R and 1206R, which have known super-high resistances, areinterposed in serial between the buffer amplifiers 1204 and 1206 and theDUT-side force terminal. The resistance of an impedance 1208 is lowcompared to the super-high resistors 1204R and 1206R. The impedance 1208is connected to an input of the buffer 1202, so that almost no currentflows in the impedance 1208. Thus, micro current that flows through thecore line of the connector 124F adjacent to the DUT 50 flows via thesuper-high resistor 1204R or 1206R. At this point, the resistance of thesuper-high resistance 1204R or 1206R, which causes a voltage drop, isvery high and thus causes a voltage drop that can be measured even formicro current at a level of attoampere. The first buffer amplifiers 1210and 1212 are connected to outputs of the buffer amplifiers 1204 and1206, respectively. The micro-current detector 120 uses the first bufferamplifiers 1210 and 1212 and the second buffer amplifier 1202 totransmit a voltage across the super-high resistor 1204R or 1206R to thecable 214 or 218. In this manner, the micro-current detector 120 isconfigured such that the SMU 20 measures a voltage across the super-highresistor 1204R or 1206R, whose resistor is known, thus making itpossible to accurately measure micro current in the vicinity of the DUT50. A voltage output from the buffer amplifier 1202 is transmitted tothe SMU 20 via the cable 214 or 218, and is also used to perform controlso that a voltage at the connector 124F reaches a desired value, whenthe SMU 20 applies a voltage to the terminal 1214.

Referring to FIG. 8, a wire (a first input) that provides a connectionamong the upper contact of the switch S6, the super-high resistor 1204R,the super-high resistor 1206R and the upper contact of the switch S5 anda wire (a second input) that provides a connection between the lowercontact of the switch S6 and the positive-side input of the bufferamplifier 1202 serve as inputs for the micro-current detector 120. Inaddition, a wire (a first output) that sends an output of the bufferamplifier 1202 as a part of the cables 214 and 218 and a wire (a secondoutput) that sends an output of one of the first buffer amplifiers 1210and 1212 through switching performed by the switch S10 serve as outputsfor the micro-current detector 120.

[For Supplying High-speed Pulse to DUT]

The present invention can be used to achieve both capacitancemeasurement and high-accuracy DC measurement, and is also effectivelyused for a case in which a pulse generator is used. A configuration fora case in which a pulse generator is used will be described next withreference to FIG. 9.

In FIG. 9, this pulse generator 24 has a first channel 241 and a secondchannel 242. The first channel 241 and the second channel 242 areconnected to corresponding measuring-means-side connectors 122L+ of theASUs 12P and 12M via coaxial cables 24P and 24M, respectively. Thetransmission of a signal from the first channel 241 of the pulsegenerator 24 will now be described. Inside the ASU 12P, the centerconductor of the cable 24P is electrically connected to the centerconductor of the triaxial cable 30F via the switches S1 and S2. Theouter shield conductor of the coaxial cable 24P is electricallyconnected to the guard conductor of the triaxial cable 30F via theswitch S1. With this arrangement, a feedback path is also realized for apath supplying a high-speed pulse to the positive side of the DUT 50.The connection for realizing the feedback path is realized by openingand closing of the switches S1 and S2 under the control of thecontrolling means 202. With this arrangement, a frequency-band-dependentdifference of the length of the feedback paths is eliminated.Conventionally, due to skin effect, high-frequency components returnthrough the outer shield conductor of a coaxial cable corresponding tothe signal line. In such a case, the path through which thehigh-frequency components pass is different from a path forlow-frequency components, thus causing fluctuation of a waveform.

Even with the pulse generator 24, merely controlling the switches makesit possible to switch to a path for DC measurement. The switching isachieved by, for example, causing the controlling means 202 of the SMU20 to open the upper channel for the switch S2 and to close all thechannels for the switch S6 and the upper channel for the switch S5. Inthis case, either one of the SMU 20 or the micro-current detector 120can detect current, in the same manner as the case for measuring a DCcomponent.

While FIG. 4 illustrates the switches S3 and S4 and the connector 122Pfor the pulse generator 24, the description here is given for the caseof the connector 122L+, since it is clear that the connector 122P iselectrically equivalent to the connector 122L+. Thus, the sameconfiguration can be possible even when the switches S3 and S4 and theconnector 122P for the pulse generator 24 are used. Although the abovedescription has been given using the first channel 241 of the pulsegenerator 24 and the ASU 12P, the cable 24M and the ASU 12M, whichoperates in the same manner as the ASU 12P, may be used to allow ahigh-speed pulse to be applied to the negative side of the DUT 50 viathe second channel 242 of the pulse generator 24.

[Configuration of Single Channel for Supplying High-speed Pulse to DUT]

FIG. 10 shows a configuration in which only the first channel 241 of thepulse generator 24 is used to apply a pulse to the DUT 50 and the SMU 20is used to perform measurement, while the probe apparatus 100 probesthree connectors of the DUT 50. In this case, a description is given ofan example in which the DUT 50 is an IGFET (insulated gate field-effecttransistor). The first channel of the SMU 20 serves to control the ASU12P in this case. Thus, the cable 214 is connected to allow control ofthe ASU 12P.

One end of the center conductor of the coaxial cable 24P is connected toa signal line of one channel of the pulse generator 24, and the otherend of the center conductor is electrically connected to the centerconductor 302 of the triaxial cable 30F via the connector 122L+ and theswitches S1 and S2 of the ASU 12P. The center conductor 302 of thetriaxial cable 30F is electrically connected a positive-side gateelectrode of the DUT 50. One end of the outer shield conductor of thecoaxial cable 24P is connected to a common line of the channel of thepulse generator 24, and the other end of the outer shield conductor iselectrically connected to the guard conductor 306 of the triaxial cable30F via the connector 122L+ and the switch S1 of the ASU 12P. The guardconductor 306 of the triaxial cable 30F is electrically connected to anegative-side source electrode of the DUT 50 via the switch S9 that isclosed. The triaxial cable 216, which is connected to the second channelof the SMU 20, is electrically connected to a negative-side drainelectrode of the DUT 50. With such connections, a pulse can be appliedto the DUT 50 by using only the first channel 241 of the pulse generator24 to allow the SMU 20 to perform measurement.

Also in this case, as described with reference to FIG. 7, DC componentscan be measured with the SMU 20. In this case, in the configurationshown in FIG. 10, the controlling means 202 of the SMU 20 performscontrol so as to open all the switches S1 and S2, to close the switchesS5 and S6, and to open the switch S9. In this case, in FIG. 10,measurement is performed on the section between the positive-side gateelectrode and the negative-side drain electrode of the DUT 50 but not onthe source electrode thereof. Which of the measurement terminals areprobed can be selected as needed. As in the case of FIG. 7, it ispossible to perform measurement using the detecting means of the SMU 20and measurement using the micro-current detector 12 constituted by theASUs 12P and 12M.

[Measurement Using Preamplifier]

Next, a connection apparatus, which uses preamplifiers, according to anembodiment of the present invention will be described with reference toFIG. 11. In this embodiment, preamplifiers 600 and 601 are provided toamplify current or voltage signals to be supplied to the first measuringmeans. Amplifiers or the like that amplify current and/or a voltage canbe used for the preamplifiers 600 and 601. The preamplifiers 600 and 601are connected to the switching means 12P and 12M, respectively.Connectors (first connecting means) 602 and connectors (secondconnecting means) 604 are provided in this embodiment. The connectors602 are connected to the respective preamplifiers 600 and 601 and arealso connected to the first measuring means (e.g., the SMU 20) formeasuring a first electrical characteristic of the DUT 50. Theconnectors 604 are connected to the switching means and are alsoconnected to the second measuring means (e.g., the LCR meter 22) formeasuring a second electrical characteristic of the DUT 50. Theswitching means 12 can perform switching such that either the connectors602 or the connectors 604 are electrically connected to the DUT 50, inaccordance with the switching signal sent from the controlling means202.

Some illustrative embodiments according to the present invention havebeen described in the above. It is apparent to those skilled in the artthat various improvements can be made to the embodiments withoutsubstantially departing from the novel disclosure and advantages of thepresent invention. It is, therefore, intended that such improvements arealso encompassed by the claims of the present invention.

1-16. (canceled)
 17. A connection apparatus comprising: a first triaxialconnector and a second triaxial connector that are to be connected to adevice under test, which is a semiconductor device; a first coaxialconnector, a second coaxial connector, and a third triaxial connectorthat are to be connected to measuring means for measuring an electricalcharacteristic of the device under test; micro-current detecting meanscomprising a first output, a second output, a first input, a secondinput, resistors connected to the first input, and a buffer amplifierfor transmitting respective voltages across the resistors to the firstoutput and the second output; switching means for switching betweenconnection configurations connected to the first coaxial connector, thesecond coaxial connector, and the third coaxial connector; and a controlinput terminal that is connectable to controlling means for controllingthe switching means; wherein, for measuring alternating current, undercontrol of the controlling means through the control input terminal, theswitching means establishes connections such that core lines of thefirst and second coaxial connectors are interconnected and are connectedto the core line of the first triaxial connector, and outer shieldconductors of the first and second coaxial connectors are interconnectedand are connected to guard conductors of the first and second triaxialconnectors, each guard conductor being disposed between the core lineand an outer shield conductor of each triaxial connector; wherein, formeasuring direct-current voltage current, the switching meansestablishes connections such that a core line of the third triaxialconnector is connected to the core line of the first triaxial connector,the core line of the second triaxial connector is connected to the firstoutput via the second input of the micro-current detecting means, and aguard connector of the third triaxial connector is connected to theguard conductors of the first and second triaxial connectors; andwherein, for measuring micro current, the switching means establishesconnections such that the core line of the first triaxial connector isconnected to the first input of the micro-current detecting means tocause the buffer amplifier to output the respective voltages across theresistors as first and second outputs.
 18. The connection apparatusaccording to claim 17, further comprising a signal feedback terminal forconnecting the outer shield conductors of the first and second coaxialconnectors to outside, when neither of the guard conductors of the firstand second triaxial connectors is connected to a feedback path requiredfor measuring the electrical characteristic.